Radium
alkaline earthProperties
| Property | Value |
|---|---|
| Atomic Mass | 226 amu |
| Category | alkaline earth |
| Group | 2 |
| Period | 7 |
| Electron Configuration | [Rn] 7s2 |
| Electronegativity | 0.9 (Pauling) |
| Oxidation States | 2 |
| Melting Point | 973 K (699.9 °C) |
| Boiling Point | 2010 K (1736.8 °C) |
| Density | 5.5 g/cm³ |
| Discovered By | Marie Curie, Pierre Curie (1898) |
About Radium
Radium is the heaviest alkaline earth and behaves like a more radioactive barium — same Ra²⁺ chemistry, similar solubilities, similar bone-seeking biology. Marie and Pierre Curie isolated it in 1898 by processing tonnes of pitchblende residue from the St. Joachimsthal mines, a job that took them four years of fractional crystallization to get a tenth of a gram of RaCl₂. Activity per gram is about a million times that of uranium, enough that the salts glow faintly blue from air ionization and warm themselves measurably above ambient. The early-1900s radium craze put it into watch dials, tonics, and 'Radithor' patent medicines, killing customers and the Radium Girls dial-painters whose jaws decayed from ingested ²²⁶Ra. The same bone affinity now drives ²²³Ra (Xofigo) therapy: alpha emissions from radium that has parked itself in metastatic bone lesions deliver lethal dose at micron range while sparing marrow.
Fun Fact
Marie Curie's personal effects, including her notebooks and even her cookbook, remain so radioactive from radium contamination that they are stored in lead-lined boxes and require protective equipment to handle, over 90 years after her death.
Common Uses
- ²²³RaCl₂ (Xofigo) targeted alpha therapy for castration-resistant prostate cancer bone metastases
- Ra-Be neutron sources where (α,n) reactions on beryllium produce ~13 MeV neutrons
- Historical zinc sulfide phosphor activator for self-luminous dial paint
- Calibration standard for high-activity gamma detectors
- Geochemical tracer for groundwater age and radon flux studies
- Teaching specimen for demonstrating alpha decay chains